Quote Originally Posted by rabernet
Yes, between the glass and the flexwatt
You can do it either way. My probe is actually in the tank, taped to the bottom, so I've got flex-glass-probe. I do it that way because I feel that with the probe in contact with the flex, it will sense the temp too quickly, which will make the t-stat click on and off more than is necessary. Other people do it other ways. You don't want the probe unsecured whatever you do. If it is, the snake could move it, causing low readings to the t-stat, and overheating of the flex. What you need to check, whether the probe is inside the tank, or under sandwiched between the glass and flex, is the temp on top of the substrata. I use aspen in all my cages, and it absorbs some of the heat from the flex. So, my t-stats are usually set 10-15 degrees higher than what my temp gun tells me the surface of the aspen is. In Tigerlilly's tank hot side t-stat is set at 106, and I'm reading 92 on top of the aspen. Obviously, the more substrata you've got, the higher you'll have to bump your t-stat setting.

As an aside, I had a wired one foot piece of flex that I just plugged in to see how hot it actually got, in 15 minutes it was at 147 degrees according to my Fluke temp gun.